This invention relates to ball throwing devices, and in particular, to a portable net and robot for recycling and sequentially serving a plurality of table tennis balls to a player at adjustable rates and trajectories. While the invention is described with particular emphasis on the application to table tennis robots, those skilled in the art will recognize the wider applicability of the inventive principles disclosed hereinafter.
Various devices for serving balls to players, for practice or for sport, in games such as table tennis, tennis, and baseball are well known in the prior art. For example, the U.S. Pat. No. 2,087,575, to Littell et al, issued July 20, 1937, describes devices that can be employed in table tennis, for example, for ejecting lightweight balls. The device disclosed in Littell includes an overhead supply means, typically in the form of an overhead hopper. The overhead hopper is fed by a conveyor system having a series of ball carrying members mechanically mounted for movement in a continuous loop.
U.S. Pat. No. 2,508,461, to Lemon, issued May 23, 1950, describes an apparatus for ejecting table tennis balls employing pressurized air, as from a home vacuum cleaner, to propel and eject the balls from a conduit. A gravity fed collector box is provided for introducing a ball into a lower portion of the conduit. The Lemon device provides no control on the entrance of the balls, and failure of the balls to feed properly can result in a loss of air pressure particularly as a plurality of balls are introduced into the system.
U.S. Pat. No. 3,917,265, to Schrier et al, issued Nov. 4, 1975, is another pneumatic ball ejecting machine including pneumatic means for transporting the balls from a collection source, for loading the balls to an ejection means and for ejecting the balls. Again, maintenance of air pressure in the device is critical. The ejection means includes a plurality of barrels mounted at fixed angles with respect to each other so as to provide a predetermined number of variations in the trajectories of the ejected balls. The spin on an ejected ball is imparted through random contact between the ball and the wall of a particular barrel as the ball is propelled through that barrel. This results in a uncontrollable assortment of spins.
The U.S. Pat. No. 4,116,438, to Berliner, issued Sept. 26, 1978, describes a device for throwing table tennis balls, having a mechanical throwing means including two flexible, thin throwing discs extending generally parallel with respect to each other, for grasping a table tennis ball between them and ejecting it along a guide. The material properties of the discs thus are important considerations, due to the repeated flexure of the discs. Balls also are returned to the serving discs by a pneumatic means. The U.S. Pat. No. 2,793,636, to Cook, issued May 28, 1957, describes a fan operated device, as does the U.S. Pat. No. 3,911,888, to Horvath, and the U.S. Pat. No. 3,989,245, to Augustine.
The U.S. Pat. No. 3,794,011, to Newgarden, issued Feb. 26, 1974, describes a relatively simple device for imparting variations in the amount of spin applied to a ball being served by a server. The disclosure of the Newgarden patent is intended to be incorporated herein by reference.
While all of these prior art devices, and others in the art, work for their intended purposes, it is evident from the large number of these devices, that no one device has solved the problems of providing a low cost, reliable, and relatively uncomplicated automatic serving device for table tennis. Pneumatic devices are inherently unreliable. Mechanically operated devices have been relatively complex if full functions were to be provided. Even when mechanical devices were simplified, they lacked the ability to provide a full range of shots for practice or sport.
The invention disclosed hereinafter overcomes these prior art deficiencies by providing a relatively low cost, simple to construct robot that provides a full range of play both for practice and for sport. The robot, in combination with a return net, provides for automatic replay of balls returned by player. The device construction provides mechanical simplicity, low cost, and a wide range of shot capabilities.
One of the objects of this invention is to provide a portable table tennis ball serving device which closely emulates the variety of serves expected from a human competitor.
Another object of this invention is to provide an elevated serving device which is automatically supplied with balls from the level of a playing surface, without the need of overhead hoppers.
Another object of this invention is to provide a table tennis ball serving device which will not cause excessive wear or deformation of the balls during the course of operation of the device.
Another object of this invention is to provide a ball serving device which can be regulated remotely from the ball serving device;
Yet another object of this invention is to provide a ball serving device which is relatively easy to set-up and remove from a set-up condition.
Another object of this invention is to provide a table tennis ball serving device which will precisely duplicate various combinations of ball velocity, spin and trajectory, as well as adjustable rates of serve, in order to permit repeated practice of a particular shot or return.
Another object of this invention is to provide a ball throwing device of flexible operation and performance, but of relatively simple and inexpensive construction.
Another object of this invention is to provide a ball throwing device having component parts which are not subject to excessive wear during extended use.
Another object of this invention is to provide a ball serving device which will recycle returned balls to permit continuous practice or play with a minimum number of balls.
Another object of this invention is to provide a ball serving device which will automatically vary the trajectory of a served ball through a predictable pattern.
Another object of this invention is to provide a robot serving device which has a controllable panning pattern for the serving head.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.